In a Long Term Evolution (LTE) system, a physical uplink control channel (PUCCH) occupies, for sending uplink control information (UCI), 13 or 14 orthogonal frequency division multiplexing (OFDM) symbols or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) symbols in one subframe. A PUCCH format 1a/1b is used to transmit response information of 1 or 2 bits, and the PUCCH format 1a/1b is sent in a sequence modulation manner. Generally, in the LTE system, to avoid interference between PUCCHs in two neighboring cells, sequences selected for the neighboring cells need to have a low correlation with each other. To expand coverage of a PUCCH, it is necessary to ensure that all sent signals have relatively small peak to average power ratio (PAPR) values and cubic metric (CM) values.
Currently, in the LTE system, there are 30 existing length-N root sequences xi, i=0, 1, . . . , N−1, where N=12, 18, 24, or 6. The root sequence is used for sending UCI or a demodulation reference signal (DMRS) by using a PUCCH format 1a/1b in the LTE system. However, in preliminary design of the LTE system, optimization of the CM value and the sequence correlation is mainly considered for the 30 length-N root sequences. A relationship between the CM value and the PAPR value is: the PAPR may not be small if the CM value is small. Therefore, it cannot be ensured that PAPR values are small when it is ensured that all the 30 length-N root sequences have relatively small CM values and low correlations.
A length-24 CGS in LTE has a relatively large PAPR, and PAPR values are as follows:
3.4088, 3.7273, 3.5504, 3.5747, 3.6863, 3.5919, 3.9650, 3.8684, 4.2962, 3.2399, 4.1349, 2.9308, 3.3087, 4.0994, 3.7059, 3.7320, 4.0424, 4.0889, 3.0390, 3.4151, 3.9811, 4.2336, 4.1542, 3.5316, 2.8697, 2.6239, 3.2999, 3.8447, 3.8657, and 3.7505.
PAPRs of length-18 sequences in LTE are as follows: 3.3052, 3.0602, 3.2669, 3.7847, 3.5747, 3.6053, 3.3331, 3.1714, 3.1280, 3.7510, 2.9786, 3.4392, 3.0917, 3.6472, 3.4528, 3.4566, 3.8168, 3.1846, 3.0146, 3.4002, 3.1365, 3.7687, 3.1833, 3.9640, 3.9144, 3.4006, 3.4189, 3.6522, 2.8956, and 3.8309.
PAPRs of length-6 sequences in LTE are as follows: 3.5139, 3.5139, 4.1492, 3.0076, 4.0755, 4.2597, 4.1492, 4.1492, 2.9721, 3.1240, 4.2597, 4.2597, 4.0755, 3.0076, 4.0755, 2.8129, 2.9721, 4.1492, 3.0076, 3.0076, 4.1492, 2.8129, 3.0076, 3.5139, 3.5139, 4.0755, 4.1492, 4.1492, 4.0755, and 4.2597. It can be seen that not a few PAPR values are greater than 3 dB.